Long term economic and environmental concerns with the current petroleum-based economy have driven the development of approaches that convert renewable sources to organic chemicals to replace those derived from petroleum feed stocks. Production of biofuels, such as ethanol or butanol, through microorganisms has been a research focus in recent years and significant progress has been made in this area. At the same time, there remains a great need for development of biorefining processes that utilize microorganisms to convert renewable sources into industrially useful non-alcohol chemicals.
Aldehydes, in particular, are in great demand because they are usually quite reactive and can serve as building blocks or precursors for other chemicals. For example, isobutyraldehyde can be used to produce isobutanol, isobutyric acid, acetal and oxime, for various industrial purposes. Many microorganisms, such as E. coli, can convert aldehydes to alcohols through alcohol dehydrogenases (ADHs). However, due to the robust endogenous alcohol dehydrogenase and/or aldehyde reductase activity, aldehydes are efficiently converted to alcohols in E. coli with intact ADHs, and the natural net production of aldehydes or non-alcohol aldehyde derivatives, such as carboxylic acids, is usually low.
Isobutyraldehyde, in particular, is an important commodity chemical; it serves as a type of fragrance and can be used as a flavor additive, as well as in the production of plasticizers. Many microorganisms, such as E. coli, robustly convert aldehydes, such as isobutyraldehyde, into alcohols via alcohol dehydrogenase and/or aldehyde reductase activity. Isobutyraldehyde is converted to isobutanol via the action of isobutyraldehyde reductase (IBR) activity. Isobutyraldehyde reductase belongs to the broad class of alcohol dehydrogenase enzymes.
In view of these facts and the growing global demand for non-alcohol chemicals produced from renewable sources, a significant need exists for more productive recombinant microorganisms and improved methods for synthesis of these chemicals. Specially, recombinant E. coli and other bacteria are needed for cost-efficient biosynthesis of aldehydes and other non-alcohol chemicals that can be further derived from aldehydes.